Conventionally, a physical quantity detector configured to detect a physical quantity has been proposed in, for example, Patent Literature 1. The detector includes a thin diaphragm which can be deformed in response to the application of a physical quantity and multiple strain gauges whose resistance value changes by distortion in response to the distortion of the diaphragm. The individual strain gauges are connected so as to form a bridge circuit portion.
The detector includes the two bridge circuit portions described above. Accordingly, it is possible to determine that either one of the bridge circuit portions has suffered a failure or characteristic fluctuations when a difference between physical quantities based on respective output signals from the two bridge circuit portions exceeds a normal range.